Torque limiter

ABSTRACT

A torque limiter for limiting the torque which can be applied by an input shaft to an output shaft and comprising a fixed outer race, a cage within the race constituting the output member of the limiter, a cam constituting the input member of the limiter and normally operative to drive the cage by cooperation with one or more rollers confined by the cage and a torsion spring connected between the cam and the cage, the spring yielding, when excessive torque is reacted by the driven mechanism, to cause the cam to displace the roller or rollers into locking engagement with the outer race.

ite States tet Neal et al.

[ Feb.8,l972

[54] TORQUE LIMHTER [73] Assignee: H. M. Robson Limited, London, England[22] Filed: July 10, 1970 [21] Appl. No.: 53,927

[56] References Cited UNITED STATES PATENTS 2,668,426 2/1954 Hoover"64/29- 3,499,511 3/1970 Bouhot 1 88/134 X 3,468,403 9/1969 Nasvytis..l88/134 X 3,542,162 11/1970 Kerr 1 88/134 Primary Examiner-Edward G.Favors Attorney-4E. T. be Gates and Martin Kirkpatrick [57] ABSTRACT Atorque limiter for limiting the torque which can be applied by an inputshaft to an output shaft and comprising a fixed outer race, a cagewithin the race constituting the output member of the limiter, a camconstituting the input member of the limiter and normally operative todrive the cage by cooperation with one or more rollers confined by thecage and a torsion spring connected between the cam and the cage, thespring yielding, when excessive torque is reacted by the drivenmechanism, to cause the cam to displace the roller or rollers intolocking engagement with the outer race.

3 Claims, 3 Drawing Figures TORQUE LIMITER This'invention provides atorque limiter for limiting the torque which can be applied by an inputshaft to an output shaft and comprising a fixed outer race, a cagewithin the race constituting the output member of the limiter, a camconstituting the input member of the limiter and normally operative todrive the cage by cooperation with one or more rollers confined by thecage and a torsion spring connected between the cam and the cage, thespring yielding, when excessive torque is reacted by the drivenmechanism, to cause the cam to displace the roller or rollers intolocking engagement with the outer race. The input torque is then stalledto earth.

One embodiment of torque limiter according to the invention isillustrated, by way of example, in the accompanying drawing, in which:

FIG. 1 is a longitudinal section,

FIG. 2 is a section on the line Illl in H6. 1, showing the limiter inthe driving position, and

FIG. 3 is a similar view showing the limiter locked.

The torque limiter illustrated includes a cam 10, constituting the inputmember, a plurality of rollers 11, a roller cage 12 constituting theoutput member, a fixed outer race 13 and a torsion spring 14 connectedbetween the input member 10 and the output member 12. The torsion spring14 is shown as a torsion bar but it could alternatively be a wound coilspring. In use the input member 10 is connected to an input shaft andthe output member 12 to an output shaft.

Under normal conditions a straight through drive is obtained, asindicated in FIG. 2. When driving torque is applied to the input member,torque load is applied to the output member. The torque transmitted istherefore felt by the torsion spring 14 which will deflect when excesstorque is reacted by the driven mechanism to cause relative rotation ofthe cam 10 and the cage 12 to the position shown in FIG. 3 in which theballs 11 are forced outwardly to lock in the wedge angles between thecam 10 and the outer race 13, so stalling the input torque.

As will be apparent, the torque limiter operates for both directions ofrotation of the input member. it is resetting in the sense that if,after the input has been stalled, the reacted torque falls to apredetermined level, it will revert to a straight through drive.

The torque limiter could, alternatively, be so designed to maintain itsonce locked condition until the input torque is deliberately reduced orreversed.

The torque limiter may be an independent unit, or it may be incorporatedin the driving unit or the driven unit.

If desired,'the torsion spring may be preloaded. The torque limiter willthen work exactly as above but because the spring is preloaded, allvalues of torque which are lower than the preload will be transmittedwithout deflecting the torsion spring. If the torque level exceeds thespring preload the spring will deflect and the rollers will lock in thewedge angles as before.

What we claim as our invention and desire to secure by Letters Patentis:

1. A torque limiter for limiting the torque which can be applied by aninput shaftto an output shaft and comprising a fixed outer race, a cagewithin the race constituting the output member of the limiter, a camconstituting the input member of the limiter and normally operative todrive the cage by cooperation with at least one roller confined by thecage, and means including torsion spring connected between the cam andthe cage for causing the cam to displace the roller into lockingengagement with the outer race when excessive torque is applied by theinput shaft.

2. A torque limiter according to claim 1, wherein the torsion spring isa torsion bar.

3. A torque limiter according to claim 1, wherein a plurality of rollersare confined by the cage, the torsion spring is a torsion bar, and themeans displaces the rollers into locking engagement with the outer racewhen excessive torque is reacted by the input shaft.

1. A torque limiter for limiting the torque which can be applied by aninput shaft to an output shaft and comprising a fixed outer race, a cagewithin the race constituting the output member of the limiter, a camconstituting the input member of the limiter and normally operative todrive the cage by cooperation with at least one roller confined by thecage, and means including torsion spring connected between the cam andthe cage for causing the cam to displace the roller into lockingengagement with the outer race when excessive torque is applied by theinput shaft.
 2. A torque limiter according to claim 1, wherein thetorsion spring is a torsion bar.
 3. A torque limiter according to claim1, wherein a plurality of rollers are confined by the cage, the torsionspring is a torsion bar, and the means displaces the rollers intolocking engagement with the outer race when excessive torque is reactedby the input shaft.